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The visual system is exquisitely adapted to the task of extracting conceptual information from visual input with every new eye fixation, three or four times a second. Here we assess the minimum viewing time needed for visual comprehension, using rapid serial visual presentation (RSVP) of a series of six or 12 pictures presented at between 13 and 80 ms per picture, with no interstimulus interval. Participants were to detect a picture specified by a name (e.g., smiling couple) that was given just before or immediately after the sequence. Detection improved with increasing duration and was better when the name was presented before the sequence, but performance was significantly above chance at all durations, whether the target was named before or only after the sequence. The results are consistent with feedforward models, in which an initial wave of neural activity through the ventral stream is sufficient to allow identification of a complex visual stimulus in a single forward pass. Although we discuss other explanations, the results suggest that neither reentrant processing from higher to lower levels nor advance information about the stimulus is necessary for the conscious detection of rapidly presented, complex visual information.

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Detecting meaning in RSVP at 13 ms per picture

Mary C. Potter & Brad Wyble & Carl Erick Hagmann &

Emily S. McCourt

Published online: 28 December 2013

#Psychonomic Society, Inc. 2014

Abstract The visual system is exquisitely adapted to the task

of extracting conceptual information from visual input with

every new eye fixation, three or four times a second. Here we

assess the minimum viewing time needed for visual compre-

hension, using rapid serial visual presentation (RSVP) of a

series of six or 12 pictures presented at between 13 and 80 ms

per picture, with no interstimulus interval. Participants wereto

detect a picture specified by a name (e.g., smiling couple )that

was given just before or immediately after the sequence.

Detection improved with increasing duration and was better

when the name was presented before the sequence, but per-

formance was significantly above chance at all durations,

whether the target was named before or only after the se-

quence. The results are consistent with feedforward models,

in which an initial wave of neural activity through the ventral

stream is sufficient to allow identification of a complex visual

stimulus in a single forward pass. Although we discuss other

explanations, the results suggest that neither reentrant process-

ing from higher to lower levels nor advance information about

the stimulus is necessary for the conscious detection of rapidly

presented, complex visual information.

Keywords Picture perception . Feedforward processing .

Attentionalset . Conscious perception . Conceptualprocessing

Our eyes move to take in new information three or four times a

second, and our understanding of the visual input seems to

keep pace with this information flow. Eye fixation durations

may be longer than the time required to perceive a scene,

however, because they include time to encode the scene into

memory and to plan and initiate the next saccade. Indeed, a

picture as brief as 20 ms is easy to see if it is followed by a

blank visual field (e.g., Thorpe, Fize, & Marlot, 1996 ). How-

ever, presenting another patterned stimulus after the target as a

mask interferes with processing, particularly if the mask is

another meaningful picture (Intraub, 1984; Loftus, Hanna, &

Lester, 1988 ; Loschky, Hansen, Sethi, & Pydimarri, 2010;

Potter, 1976). With rapid serial visual presentation (RSVP)

of colored photographs of diverse scenes, each picture masks

the preceding one, so only the last picture is not masked.

Nonetheless, viewers can detect a picture presented for

125msinanRSVPsequencewhentheyhaveonlybeengiven

a name for the target, such as picnic or harbor with boats

(Intraub, 1981; Potter, 1975 , 1976 ; Potter, Staub, Rado, &

O' Connor, 2002 ). Here, we tested the limits of viewers'

detection ability by asking them to look for or recall named

targets in sequences of six (Exp. 1 )or12(Exp.2 ) pictures that

they had never seen before, presented for durations between

13 and 80 ms per picture.

One reason for using such short durations was to investi-

gate the possibility that the visual system has been configured

by experience to process scene stimuli directly to an abstract

conceptual level, such as " apicnic. "In feedforward compu-

tational models of the visual system (Serre et al., 2007a ; Serre,

Oliva, & Poggio, 2007b ), the units that process a visual

stimulus are hierarchically arranged: Units representing small

regions of space (receptive fields) in the retina converge to

Electronic supplementary material The online version of this article

(doi:10.3758/s13414-013-0605-z) contains supplementary material,

which is available to authorized users.

M. C. Potter : C. E. Hagmann : E. S. McCourt

Department of Brain and Cognitive Sciences, Massachusetts Institute

of Technology, Cambridge, MA, USA

B. Wyble

Department of Psychology, Pennsylvania State University, College

Park, PA, USA

M. C. Potter (*)

Department of Brain and Cognitive Sciences, 46-4125

Massachusetts Institute of Technology, 77 Massachusetts Avenue,

Cambridge, MA 02139, USA

e-mail: mpotter@mit.edu

Atten Percept Psychophys (2014) 76:270 –279

DOI 10.3758/s13414-013-0605-z

represent larger and larger receptive fields and increasingly

abstract information along a series of pathways from V1 to

inferotemporal cortex, and higher to the prefrontal cortex. A

lifetime of visual experience is thought to tune this hierarchi-

cal structure, which acts as a filter that permits the categori-

zation of objects and scenes with a single, forward pass of

processing. In this model, even a very brief, masked presen-

tation might be sufficient for understanding a picture.

A widely accepted theory of vision, however, is that per-

ception results from a combination of feedforward and feed-

back connections, with initial feedforward activation generat-

ing possible interpretations that are fed back and compared

with lower levels of processing for confirmation, establishing

reentrant loops (Di Lollo, 2012; Di Lollo, Enns, & Rensink,

2000; Enns & Di Lollo, 2000 ; Hochstein & Ahissar, 2002 ;

Lamme & Roelfsema, 2000 ). Such loops produce sustained

activation that enhances memory. It has been proposed that we

become consciously aware of what we are seeing only when

such reentrant loops have been established (Lamme, 2006 ). A

related suggestion is that consciousness arises from "recurrent

long-distance interactions among distributed thalamo-cortical

regions" (Del Cul, Baillet, & Dehaene, 2007 ,p.2408).This

network is ignited as reentrant loops in the visual system are

formed (Dehaene, Kergsberg, & Changeux, 1998 ;Dehaene&

Naccache, 2001; Dehaene, Sergent, & Changeux, 2003 ;see

also Tononi & Koch, 2008 ). It has been estimated that reen-

trant loops connecting several levels in the visual system

would take at least 50 ms to make a round trip, which would

be consistent with stimulus onset asymmetries (SOAs) that

typically produce backward masking.

Thus, when people view stimuli for 50 ms or less with

backward pattern masking, as in some conditions in the pres-

ent study, the observer may have too little time for reentrant

loops to be established between higher and lower levels of the

visual hierarchy before earlier stages of processing are

interrupted by the subsequent mask (Kovacs, Vogels, &

Orban, 1995 ; Macknik & Martinez-Conde, 2007 ). In that

case, successful perception would primarily result from the

forward pass of neural activity from the retina through the

visual system (DiCarlo, Zoccolan, & Rust, 2012; Hung,

Kreiman, Poggio, & DiCarlo, 2005 ; Perrett, Hietanen, Oram,

& Benson, 1992 ; Thorpe & Fabre-Thorpe, 2001 ). In support

of the possibility of feedforward comprehension, Liu, Agam,

Madsen, and Kreiman (2009 ) were able to decode object

category information from human visual areas within

100 ms after stimulus presentation.

An open question is what level of understanding is

achieved in the initial forward wave of processing. One be-

havioral approach to assessing how much is understood in the

feedforward sweep is to measure the shortest time to make a

discriminative response to a stimulus. Studies by Thorpe,

Fabre-Thorpe, and their colleagues (see the reviews by Thorpe

& Fabre-Thorpe, 2001 , and Fabre-Thorpe, 2011 ) required

participants to make a go/no-go response to the presence of

a category such as animals (or vehicles, or faces) in photo-

graphs presented for 20 ms without a mask. They found that

differential electroencephalographic activity for targets began

about 150 ms after presentation. The shortest above-chance

reaction times (which would include motor response time)

were under 300 ms. Choice saccades to a face in one of two

pictures were even faster, as short as 100 ms (Crouzet,

Kirchner, & Thorpe, 2010 ). In another study (Bacon-Macé,

Kirchner, Fabre-Thorpe, & Thorpe, 2007), pictures with or

without animals were followed by texture masks at SOAs

between 6 and 107 ms; animal detection was at chance at 6

ms, but above chance starting at 12 ms, with performance

approaching an asymptote at 44 ms. These times suggested to

the investigators that the observers were relying on

feedforward activity, at least for their fastest responses.

A different question from that of feedback is whether a

selective set or expectation can modify or resonate with the

feedforward process (Llinás, Ribary, Contreras, &

Pedroarena, 1998), obviating the need for reentrant processing

and enabling conscious perception with presentation durations

shorter than 50 ms. It is well known that advance information

about a target improves detection. For example, in a recent

study by Evans, Horowitz, and Wolfe (2011 ), participants

viewed a picture for 20 ms, preceded and followed by texture

masks, and judged whether they saw a specified target (e.g.,

animal, beach, or street scene). Accuracy was consistently

higher when the target was specified just before the stimulus

was presented, rather than just after. Numerous studies have

shown that selective attention has effects on the visual system

in advance of expected stimuli (e.g., Cukur, Nishimoto, Huth,

&Gallant,2013 ). For example, in a recent study using

multivoxel pattern analysis (Peelen & Kastner, 2011), the

amount of preparatory activity in object-selective cortex that

resembled activity when viewing objects in a given category

was correlated with successful item detection.

To evaluate the effect of attentional set on target detection,

in the present experiments we compared two conditions be-

tween groups. In one group, the target was named just before

the sequence (providing a specific attentional set), and in the

other, the target was named just after the sequence (with no

advance attentional set). In the latter case, the participant had

to rely on memory to detect the target. Previous studies of

memory for pictures presented in rapid sequences have shown

that memory is poor with durations in the range of 100–200

ms per picture (Potter & Levy, 1969 ; Potter et al., 2002).

Given these results, and the known benefits of advance infor-

mation already mentioned, we expected that advance infor-

mation would improve performance; the question was wheth-

er it would interact with duration, such that detection of the

target would be impossible at the shorter durations without

advance information. Such a result would conflict with

the hypothesis that feedforward processing, without

Atten Percept Psychophys (2014) 76:270 –279 271

reentrance and without top-down information, is suffi-

cient for conscious identification.

Although both the feedforward and feedback models pre-

dict that performance will improve with presentation time, the

main questions addressed here were whether knowing the

identity of the target ahead of time would be necessary for

successful detection, particularly at high rates of presentation,

and whether we would observe a sharp discontinuity in per-

formance as the duration of the images was reduced below 50

ms, as is predicted by reentrant models. A seminal earlier

study (Keysers, Xiao, Földiák, & Perrett, 2001 ;seealso

Keysers et al., 2005) showed successful detection using RSVP

at a duration as short as 14 ms, but the target was cued by

showing the picture itself, and pictures were reused for a

single participant so that they became familiar. In the present

experiments, by specifying the target with a name and by

using multiple pictures in each sequence that the participants

had never seen before, we forced participants to identify the

target at a conceptual level rather than simply matching spe-

cific visual features.

Experiment 1

Method

Procedure Two groups of participants viewed an RSVP se-

quence of six pictures presented for 13, 27, 53, or 80 ms per

picture and tried to detect a target specified by a written name

(see Fig. 1 ). The one-to-four-word name reflected the gist of the

picture as judged by the experimenters. Examples are swan ,

traffic jam , boxes of vegetables, children holding hands , boat

out of water , campfire , bear catching fish ,andnarrow street .

For those in the before group, each trial began with a fixation

cross for 500 ms, followed by the name of the target for 700 ms,

and then a blank screen of 200 ms and the sequence of pictures.

A blank screen of 200 ms also followed the sequence, and then

the question " Yes o r No? " appeared and remained in view until

the participant pressed "Y " or " N" on the keyboard to report

whether he or she had seen the target. Those in the after group

viewed a fixation cross for 500 ms at the beginning of the trial,

followed by a blank screen of 200 ms and the sequence. At the

end of the sequence, another 200-ms blank screen appeared, and

then the name was presented simultaneously with the yes/no

question until the participant responded.

On trials in which the target had been presented, the par-

ticipant' s response was followed by a two-alternative forced

choice between two pictures that matched the target name.

The participant pressed the "G " or "J " keytoindicatewhether

the left or right picture, respectively, had been presented. On

no-target trials, the words " No target" appeared instead of the

pair of pictures.

Participants The 32 participants (17 women, 15 men) were

volunteers 18– 35 years of age who were paid for their partic-

ipation. All signed a consent form approved by the MIT

Committee on the Use of Humans as Experimental Subjects.

Participants were replaced if they made more than 50% false

"yes "responses, overall, on nontarget trials, because such a

high false alarm rate suggested that the participant was not

following instructions, but randomly guessing. One par-

ticipant was replaced in the before group, and three in

the after group.

Materials The stimuli were color photographs of scenes. The

pictures were new to the participants, and each picture was

presented only once. For the targets, two pictures were select-

ed that matched each target name; which one appeared in the

sequence was determined randomly. The other picture was

used as a foil in the forced choice test after each target-present

trial. The pictures were taken from the Web and from other

collections of pictures available for research use. They includ-

ed a wide diversity of subject matter: indoor and outdoor, both

with and without people. The pictures were resized to 300 ×

200 pixels and were presented in the center of the monitor on a

gray background. The horizontal visual angle was 10.3º at the

normal viewing distance of 50 cm. For the forced choice, two

300 × 200 pixel pictures were presented side by side.

Design A practice block was presented at 133 ms per picture,

followed by eight experimental blocks of trials. Across blocks,

the durations were 80, 53, 27, and 13 ms per picture, repeated

in the next four blocks. Each block contained 20 trials, includ-

ing five no-target trials. The target, which was never the first

or last picture, appeared in Serial Position 2, 3, 4, or 5,

balanced over target trials within each block. Across every

eight participants, the eight blocks of trials were rotated so that

the pictures in each block of trials were seen equally often at

each duration and in each half of the experiment.

Apparatus The experiment was programmed with MATLAB

7.5.0 and the Psychophysics Toolbox extension (Brainard,

1997) version 3, and was run on a Mac mini with a 2.4-GHz

Intel Core 2 Duo processor. The Apple 17-in. CRT monitor

was set to a 1,024 × 768 resolution with a 75-Hz refresh rate.

The room was normally illuminated. Timing errors sometimes

occur in RSVP sequences (McKeeff, Remus, & Tong, 2007).

Precision was controlled by using Wyble' s Stream package for

MATLAB. We checked the actual timing on each refresh

cycle in each of the groups, and excluded trials in which a

timing error of ±12 ms (equivalent to a single refresh of the

monitor) or greater affected the target picture or the pictures

immediately before and after the target. Since the timing

errors were random, they increased noise in the data but

did not produce any systematic bias. In Experiment 1 ,

an average of 22% of the target trials were removed in

272 Atten Percept Psychophys (2014) 76:270–279

the name-before group, and 10% were removed in the

name-after group. In Experiment 2 ,timingerrorsoc-

curred on fewer than 1% of the trials.

Analyses Repeated measures analyses of variance (ANOVAs)

were carried out on individual participants'd' measures, as a

function of before– after group and presentation duration (80, 53,

27, or 13 ms per picture). Planned paired t tests at each duration,

separated for each group, compared d' with chance (0.0). Serial

position effects were analyzed for the proportions of hits on

target-present trials (since there was no way to estimate false

"yes"es as a function of serial position, we did not use d' ).

Separate ANOVAs were carried out on the accuracy of the forced

choice responses on target-present trials, conditional on whether

the participant had responded " yes" (a hit) or " no" (a miss).

Results and discussion

The results are shown in Fig. 2 .Forthed' ANOVA of yes– no

responses (Fig. 2A ), we found main effects of name position,

F(1, 30) = 4.792, p<.05,η

G

2

= .066, and duration, F (3, 90) =

38.03, p < .001, η

G

2

= .414, as well as an interaction, F (3, 90) =

7.942, p < .001, η

G

2

= .129. As Fig. 2 shows, having the target

name presented before rather than after the sequence benefited

detection substantially at 80 ms, but not at all at 13 ms, with the

other durations falling in between. Detection improved as the

duration increased from 13 to 80 ms. Separate paired t tests, two-

tailed, showed that d' was significantly above chance (p < .001) at

each duration in each group. For the name-before group at 13 ms,

t(15) = 4.45, p< .001, SEM = 0.162; the significance of the

difference increased at each of the other durations. For the name-

after group at 13 ms, t (15) = 7.91, p < .0001, SEM =0.139,and

at 27 ms, t (15) = 5.60, p < .0001, SEM = 0.122; the significance

of the difference increased at the other two durations.

In an ANOVA of the effect of the serial position of the

target on the proportions of correct "yes" responses, the main

effect of serial position was significant, F (3, 90) = 4.417, p<

.01, η

G

2

= .023. The means were .71, .71, .69, and .75 for

serial positions 2, 3, 4, and 5, respectively, suggesting a small

recency effect. A marginal interaction with name position,

F(3, 90) = 2.702, p=.05,η

G

2

= .014, indicated that this

effect was larger when the name came after the sequence. This

was confirmed by separate analyses of serial position in the

before and after groups: Serial position was not significant in

the before group ( p= .095), but was in the after group, F (3,

45) = 11.23, p <.001,η

G

2

= .073, for which the means were

.67, .69, .67, and .75.

An ANOVA of the two-alternative forced choice re-

sults on target-present trials (Fig. 2B ) showed that ac-

curacy was high (M = .73) when participants had re-

ported " yes" tothetarget(ahit),butatchance( M=

.52) when they had reported " no" (a miss), F (1, 30) =

57.92, p < .001, η

G

2

= .253. The main effect of group

(before/after) was significant, F (1, 30) = 6.70, p <.05,

Ti me

"Flowers"

Yes or no?

Left or right?

Target

Target name Before or After sequence

"Flowers"

Fig. 1 Illustration of a trial in Experiment 1 . The target name appeared either 900 ms before the first picture or 200 ms after the last picture and the two

forced-choice pictures appeared after the participant responded "yes" or "no"

Atten Percept Psychophys (2014) 76:270 –279 273

η

G

2

= .018, and interacted with whether the response

had been " yes" or " no,"F (1, 30) = 4.63, p <.05,

η

G

2

= .026. When participants reported having seen

the target, forced choice accuracy was relatively better

in the before than in the after condition, although both were

above chance. When the target was missed, both groups were

close to chance. We found a main effect of duration, F (3,

90) = 3.76, p <.05,η

G

2

= .048, and no other significant

interactions.

The main findings of Experiment 1 are that viewers

can detect and retain information about named targets

that they have never seen before at an RSVP duration

as short as 13 ms, and that they can do so even when

they have no information about the target until after

presentation. Furthermore, no clear discontinuity in per-

formance emerged as duration was decreased from 80 to

13 ms. If reentrant feedback from higher to lower levels

played a necessary role in extracting conceptual infor-

mation from an image, one would expect an inability to

detect any targets at 27 and 13 ms, even in the before

condition, contrary to what we observed. If advance

information about the target resonated or interacted with

the incoming stimuli, accounting for successful perfor-

mance at 27 and 13 ms without reentrance, then perfor-

mance should have been near chance at those durations

in the after condition, again contrary to the results. A

feedforward account of detection is more consistent with

the results, suggesting that a presentation as short as 13

ms, even when masked by following pictures, is

sufficient on some trials for feedforward activation to

reach a conceptual level, without selective attention.

Experiment 2

One question about the results of Experiment 1 was

whether they would generalize to sequences longer than

six pictures. Given that targets were limited to only four

serial positions (excluding the first and last pictures),

could participants have focused on just those pictures,

maintaining one or more of them in working memory to

compare subsequently to the target name? In that case,

increasing the number of pictures to 12 (in Exp. 2 )

should markedly reduce the proportion detected, at least

in the name-after condition.

Method

The method was the same as that of Experiment 1 ,

except as noted.

Participants The 32 participants (22 women, 10 men) were

volunteers 18– 35 years of age, most of whom were college

students; none had participated in Experiment 1 .Theywere

paid for their participation. All signed a consent form ap-

proved by the MIT Committee on the Use of Humans as

Experimental Subjects. Participants were replaced if they

Before

After

Before

After

After

Before

Hit

Miss

Forced Choice

Detection

ab

Fig. 2 Results of Experiment 1, in which participants detected a picture

that matched a name given before or after the sequence ofsix images (N=

16 in each group). Error bars depict the standard errors of the means. (A)

d' results for yes– no responses. (B) Proportions correct on a two-

alternative forced choice between two pictures with the same name on

target-present trials, conditional on whether the participant had reported

"yes " in the detection task (labeled "Hit" )or"no " (" Miss"). Chance = .5

274 Atten Percept Psychophys (2014) 76:270–279

made more than 50% false "yes " responses, overall, on non-

target trials. No participant was replaced in the before group,

and four were replaced in the after group.

1

Design The design was like that of Experiment 1 ,withtwo

groups of participants, one with the target presented before the

sequence, the other with the target presented after. The main

difference was that trials consisted of 12 rather than six pictures.

To make the 12-picture sequences, two 6-picture sequences from

Experiment 1 were combined by randomly pairing the trials in a

given block, with the restriction that the two targets in a pair were

in the same serial position (2, 3, 4, or 5; after combination, the

two potential targets were in Serial Positions 2 and 8, or 3 and 9,

etc.). To end up with an even number of six-item sequences, we

generated two new six-picture trials per block, one with a target

and one without. Each block contained 11 trials, eight with

targets and three without. Each of the eight target serial positions

was represented once per block. Which of the two target names

was used was counterbalanced between subjects within each

group. Across participants within a group, the eight blocks of

trials were rotated so that the pictures in each block of

trials were seen equally often at each duration and in

each half of the experiment.

Results and discussion

The results are shown in Fig. 3 . The main results were similar to

those of Experiment 1 .Inthed' analysis of the yes– no re-

sponses, we found main effects of whether the name was given

before or after, F (1, 30) = 8.785, p <.01,η

G

2

= .083, and

duration, F (3, 90) = 28.67, p < .001, η

G

2

= .397. Detection was

more accurate when the name was given before the sequence

rather than after, and it improved as the duration increased from

13 to 80 ms. The interaction was not significant (p =.22).

Separate paired t tests, two-tailed, showed that d' was signifi-

cantly above chance (p <.02)ateachdurationineachgroup.

For the name-before group at 13 ms, t (15) = 3.28, p <.01,SEM

= 0.152; the significance of the difference increased at each of

the other durations. For the name-after group at 13 ms, t (15) =

2.83, p <.02,SEM = 0.155; the significance of the difference

again increased at each of the other durations.

In an ANOVA of the effect of the serial position of the

target on the proportions of correct "yes" responses, the main

effect of serial position was significant, F (7, 210) = 5.20, p<

.001, η

G

2

= .032. The means were .57, .54, .66, .76, .66, .63,

.64, and .62 for Serial Positions 2, 3, 4, 5, 8, 9, 10, and 11,

respectively, suggesting a slight disadvantage for primacy, but

no recency benefit. We found no interactions.

An ANOVA of the two-alternative forced choice results on

target-present trials (Fig. 2B ) showed that accuracy was fairly

high (M = .67) when participants had reported "yes " to the

target (a hit) but was near chance (M =.52)whentheyhad

reported "no "(a miss), F (1, 30) = 20.61, p <.001,η

G

2

=.122.

The main effect of group (before/after) was not significant,

F(1, 30) = 2.34, p= .136, η

G

2

= .018, but a marginal

interaction did emerge with whether the response had been

"yes " or "no, "F (1, 30) = 2.88, p =.10,η

G

2

= .019. As in

Experiment 1 , having the name before was only better than

having the name after when the participant reported having

seen the target; when the trial was a miss, both groups were

close to chance. We found no main effect of duration, F (3,

90) = 1.35, but did find an interaction with hit/miss,

F(3, 90) = 6.43, p< .01, η

G

2

= .064: As can be seen in

Fig. 3B, the hit benefit was larger at longer durations.

Altogether, the results of Experiment 2 replicated the main

results of Experiment 1 , but now with 12 pictures per se-

quence rather than six (see Fig. 4 ). An ANOVA compared

the d' results of the two experiments. Performance (as d' )was

significantly higher with six-picture sequences (M =1.33)

than with 12-picture sequences (M =1.06),F (1, 60) =

9.83, p <.01,η

G

2

= .057. No interactions with exper-

iment were significant.

Clearly, we can reject the hypothesis that participants could

encode only two or three pictures in working memory; otherwise,

performance would have fallen more dramatically in Experiment

2, especially in the after condition, in which participants had to

retain information about the pictures for later retrieval.

The results also demonstrate that a specific attentional

expectation is not required for extracting conceptual informa-

tion from a stream of pictures: Performance remained sub-

stantially above chance at all durations when the target was

specified after the sequence. The forced choice results indi-

cate, however, that visual details were lost at the two shorter

durations with 12 pictures to retain, even when the target was

correctly reported. In the after condition, however, the forced

choice test was slightly delayed relative to the before condi-

tion, because the participants had to read the name of the target

and scan their memory of the sequence before making a "yes"

or "no " response. This intervening processing may account

for the somewhat reduced performance in the forced choice

task in both Experiments 1 and 2 when the target name

followed the sequence.

General discussion

The results of both experiments show that conceptual under-

standing can be achieved when a novel picture is presented as

briefly as 13 ms and masked by other pictures. Even when

1

Because of the relatively large number of replaced participants in

Experiment 2' s after group, we also ran the main d' analysis with the

original 16 participants. Although d' was slightly lower with the original

group than with the replaced participants, none of the significance levels

changed, including the comparison with the before group.

Atten Percept Psychophys (2014) 76:270 –279 275

participants were not given the target name until after they had

viewed the entire sequence of six or 12 pictures, their perfor-

mance was above chance even at 13 ms, indicating that a top-

down attentional set is not required in order to rapidly extract

and at least briefly retain conceptual content from an RSVP

stream. The numbers of pictures in the sequence and their

serial positions had little effect on performance, suggesting

that pictures were processed immediately rather than accumu-

lating in a limited-capacity memory buffer for subsequent

processing. This pattern of results supports the hypothesis that

feedforward processing is sufficient for the conceptual com-

prehension of pictures.

As expected, detection was more accurate, the longer the

duration per picture. However, it was striking that no sharp

drop in detection was apparent at or below a duration of 50

ms, contrary to the predictions of feedback or reentrant models

of conscious perception (e.g., Del Cul et al., 2007 ; Lamme,

2006). Instead, performance declined gradually with shorter

durations, but remained well above chance at 13 ms. More-

over, when viewers reported that they had detected the target,

they were usually above chance in selecting it in a forced

choice between two pictures, both of which fit the target

name: That is, they remembered more about the picture than

simply the concept provided by the target name. When they

had not detected the target, their forced choice was near

chance, suggesting that the visual features of unidentified

pictures were not retained.

Although the present behavioral results cannot entirely rule

out feedback, they do present a challenge to existing reentrant

models. They also raise a further question: How can concep-

tual understanding persist long enough to be matched to a

name presented 200 ms after the offset of the final masking

picture, given that the target might have been any of the six or

12 pictures just viewed? The answer to this question may lie in

the carwash metaphor of visual processing (Moore & Wolfe,

2001; Wolfe, 2003 ), in which each stimulus is passed from

one level of processing to the next. In such a model, multiple

stimuli can be in the processing pipeline at once. At the end of

this pipeline, the stimuli, having now been processed to the

level of concept, may persist in local recurrent networks that

sustain activation for several pictures in parallel, at least

briefly. In such a model, concepts are presumably represented

in a multidimensional, sparsely populated network in which

visual masks may not be effective if they are not also concep-

tually similar to the item being masked. The finding that a

forced choice between two conceptually equivalent pictures

was above chance only if the participant correctly detected the

target is consistent with the conjecture that when feedforward

processing does not reach a conceptual level, lower levels of

representation are already masked, and no featural informa-

tion can be accessed.

The finding that observers can perceive and comprehend

conceptual information from such brief images extends pre-

vious evidence that a purely feedforward mode of processing

is capable of decoding complex information in a novel image

(e.g., DiCarlo et al., 2012 ; Serre, et al., 2007a ; Thorpe et al.,

1996). Feedforward models are consistent with a range of

neural results. For example, in a study by Keysers et al.

Before

After

After

Before

Hit

Miss

Forced Choice

Detection

ab

Fig. 3 Results of Experiment 2, in which participants detected a picture

that matched a name given before or after a sequence of 12 images (N=

16 in each group). Error bars depict the standard errors of the means. (A)

d' results for yes– no responses. (B) Proportions correct on a two-

alternative forced choice between two pictures with the same name on

target-present trials, conditional on whether the participant had reported

"yes " in the detection task (labeled "Hit" )or"no " (" Miss"). Chance = .5

276 Atten Percept Psychophys (2014) 76:270–279

(2001 ), recordings were made of individual neurons in the

cortex of the anterior superior temporal sulcus (STSa) of

monkeys as they viewed continuous RSVP sequences of

pictures; the monkeys 'only task was to fixate the screen.

Neurons in STSa that were shown to respond selectively to a

given picture at a relatively slow presentation rate of 200 ms

per picture also responded selectively (although not as

strongly) to the same picture at presentations as short

as 14 ms per image.

The present behavioral results suggest that feedforward

processing is capable of activating the conceptual identity of

a picture, even when reentrant processing has presumably

been blocked because the picture is presented briefly and is

then masked by immediately following pictures. Since partic-

ipants were capable of reporting the presence of a target under

these conditions, the results strongly suggest that reentrant

processing is not always necessary for conscious processing.

They are consistent with the possibility, however, that reen-

trant loops facilitate processing and may be essential to

comprehending the details of an image. For example, a rapid

but coarse first pass of low-spatial-frequency information may

provide global category information that is subsequently re-

fined by reentrant processing (e.g., Bar et al., 2006 ). Work

with monkeys has shown that neurons that are selective for

particular faces at a latency of about 90 ms give additional

information about facial features beginning about 50 ms later

(Sugase, Yamane, Ueno, & Kawano, 1999 ). Reentrant pro-

cessing therefore might be involved after an initial

feedforward pass (Di Lollo, 2012).

The present findings can be contrasted with those of

masked-priming studies in which the prime is not consciously

seen, although it has an effect on the response to an immedi-

ately following stimulus. In a typical experiment, a brief

presentation of a word in the range of 25– 60 ms— the

prime— is followed by a second, unmasked word, to which

the participant must respond (Dehaene et al., 2001 ; Forster &

Davis, 1984 ). If the prime is identical or related to the target

word, the response to the latter is faster and more accurate than

with no prime or an unrelated prime, even when the prime is

not consciously identified. In such studies, the participant' s

focus of attention is on the final word, whose longer duration

permits it to receive full, recurrent processing that might block

awareness of the more vulnerable information from the prime

that was extracted during the feedforward sweep. In the pres-

ent experiments, in contrast, the masking stimuli were of the

same duration as the preceding target stimulus, and all were

potential targets. In these conditions, even durations as short

as 13 ms are clearly sufficient, on a significant proportion of

trials, to drive conscious detection, identification, and imme-

diate recognition memory.

Finally, perhaps our most striking finding is that perfor-

mance was surprisingly good, even when the target name was

given only after the sequence. It has long been assumed that

the detection of rapidly presented targets in an RSVP stream

(e.g., Potter, 1976 ) is possible only because the participants

had the opportunity to configure their attentional filters in

advance (e.g., Peelen & Kastner, 2011 ). Indeed, Potter

(1976 ) found that the ability to detect an image named in

advance was much greater than the ability to recognize pic-

tures later in a yes– no test of all of the pictures mixed with

distractors. Other research (e.g., Potter et al., 2002 ) has indi-

cated that the memory traces generated by RSVP are fragile

Before - 6

Before - 12

After - 6

After- 12

Dura

Fig. 4 Comparison of the d' results of Experiment 1 (six pictures) and Experiment 2 (12 pictures). Error bars depict the standard errors of the means

Atten Percept Psychophys (2014) 76:270 –279 277

and are rapidly degraded by successive recognition testing.

When participants are given an immediate recognition test of

just one item, however, the present results show that they are

able to detect it in their decaying memory trace at a level of

accuracy not far from the accuracy when the target was

prespecified at the start of the trial. This result is consistent

with the idea that a single forward sweep as short as 13 ms is

capable of extracting a picture' s conceptual meaning without

advance knowledge. Moreover, the pictures' conceptual iden-

tities can be maintained briefly, enabling one to be matched to

a name presented after the sequence.

A possible role for such rapid visual understanding in

normal experience would be to provide nearly instantaneous

conceptual activation that enables immediate action when

necessary, without waiting to refine understanding by reen-

trant processing or by the kind of conscious reflection that

requires a stable recurrent network.

Author note This research was supported by National Institutes of

Health Grant No. MH47432. M.C.P. developed the study concept. All

of the authors contributed to the study design. The testing, data collection,

and data analysis were performed by E.S.M. and C.E.H. under the

supervision of M.C.P. and B.W. M.C.P. drafted the article, and B.W.

and C.E.H. provided critical revisions. All of the authors approved the

final version of the article for submission. We thank Chidinma Egbukichi

and Steven Yu for assistance.

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... There are many publications about human vision. It was found that vision is ideally adapted to the task of extracting conceptual information from visual input with each new fixation of the eye 3-4 times per second, thus the brain processes images in 13 ms [18]. The brain can support two functional streamsvisual and auditorywhile driving and listening to the radio or using navigation [19]. ...

The article provides an overview of risk factors that are caused by the working conditions of car drivers and provides an example of a methodology for assessing visual loads that were measured using a digital video recorder. To assess real visual loads on a car driver, a method for simultaneous recording of information of visual load and heart rate has been developed and tested. The proposed method made it possible to establish a correlation between the dynamics of the flow of visual traffic information and the response of the driver's body in the form of response changes in the pulse. The effectiveness of the method was shown and the correlation of video fragments and pulsograms with R = 0.4 was established. The results of the work are applicable to assess the working conditions of car drivers, when visual stress is a leading factor in working conditions, in order to prevent fatigue and road traffic accidents.

... Remote centralized clouds will induce high network and communication latency, which is not suitable due to the latency sensitivity of VR applications. Studies [3], [4] have shown that a latency of more than 15ms in VR can lead to motion sickness. Increased latency also breaks the immersion of the VR experience. ...

• Mostafa Abdelrahman
• Mohammed S. Elbamby
• Vilho Räisänen

Virtual Reality (VR) applications require high data rate for a high-quality immersive experience, in addition to low latency to avoid dizziness and motion sickness. One of the key wireless VR challenges is providing seamless connectivity and meeting the stringent latency and bandwidth requirements. This work proposes a proactive wireless VR system that utilizes information about the user's future orientation for proactive scheduling and caching. This is achieved by leveraging deep neural networks to predict users' orientation trained on a real dataset. The 360{\deg} scene is then partitioned using an overlapping viewports scheme so that only portions of the scene covered by the users' perceptive field-of-view are streamed. Furthermore, to minimize the backhaul latency, popular viewports are cached at the edge cloud based on spatial popularity profiles. Through extensive simulations, we show that the proposed system provides significant latency and throughput performance improvement, especially in fluctuating channels and heavy load conditions. The proactive scheduling enabled by the combination of machine learning prediction and the proposed viewport scheme reduces the mean latency by more than 80% while achieving successful delivery rate close to 100%.

Accidents resulting from poorly planned or set up work environments are a major concern within the construction industry. While traditional education and training of personnel offer well-known approaches for establishing safe work practices, serious games in virtual reality (VR) are used more often as a complementary approach for active, personalized learning experiences. Their designs yet have to take full advantage of how trainees can potentially manipulate and interact with virtual objects. In addition, little construction safety research has focused on generating and analyzing the inherent data that can be collected about the trainees' actions in the virtual environment. The objective analysis of their performance in the virtual environment offers precise feedback to sensitize their work behavior later in real practice. This research presents a novel framework for the generation and assessment of the trainees' data in augmented virtuality (AV). The proposed approach is tested in a virtual work environment consisting of multiple stages and hazards that are consistent within today's construction sites and workshops. A real angle grinder has been reworked and repurposed as an interactive AV controller to further enhance immersion. Results on the performance in the proposed system and the experiences of two groups of volunteering participants are presented and discussed. An outlook presents future avenues towards enhancing existing construction safety education and focus points on correlating objective tracking data with self-assessment.

Résumé Les recherches menées ces dernières années dans le domaine de la cognition spatiale font état d'observations empiriques originales dont l'approche « traditionnelle » parvient parfois difficilement à rendre compte. L'une des contributions majeures de ces observations a été d'inviter à repenser la perception de scènes, considérant que celle-ci bénéficierait à ne plus être appréhendée comme étant centrée principalement sur la modalité sensorielle considérée. À ce titre, le Modèle multisource de la perception de scènes (Intraub et al.) offre un cadre théorique alternatif, selon lequel la perception de scènes serait structurée autour d'un cadre spatial égocentrique, complété par différentes sources d'information (externe, interne). Toutes travailleraient de concert de façon à créer une simulation des régions environnantes probables, intégrant la vue perçue dans un contexte spatial plus large. Cette revue de question se propose notamment de présenter comment l'une des avancées du modèle d'Intraub est d'unifier différents champs de la cognition jusqu'alors appréhendés isolément.

• Sergio Cermeño-Aínsa

A central goal for cognitive science and philosophy of mind is to distinguish between perception and cognition. The representational approach has emerged as a prominent candidate to draw such a distinction. The idea is that perception and cognition differ in the content and the format in which the information is represented -just as perceptual representations are nonconceptual in content and iconic in format, cognitive representations are conceptual in content and discursive in format. This paper argues against this view. I argue that both perception and cognition can use conceptual and nonconceptual contents and be vehiculated in iconic and discursive formats. If correct, the representational strategy to distinguish perception from cognition fails.

How do spatial constraints and meaningful scene regions interact to control overt attention during visual search for objects in real-world scenes? To answer this question, we combined novel surface maps of the likely locations of target objects with maps of the spatial distribution of scene semantic content. The surface maps captured likely target surfaces as continuous probabilities. Meaning was represented by meaning maps highlighting the distribution of semantic content in local scene regions. Attention was indexed by eye movements during the search for target objects that varied in the likelihood they would appear on specific surfaces. The interaction between surface maps and meaning maps was analyzed to test whether fixations were directed to meaningful scene regions on target-related surfaces. Overall, meaningful scene regions were more likely to be fixated if they appeared on target-related surfaces than if they appeared on target-unrelated surfaces. These findings suggest that the visual system prioritizes meaningful scene regions on target-related surfaces during visual search in scenes.

• Harrison Adler
• Helene Intraub

A black frame presented around one of 12 pictures during rapid serial visual presentation (RSVP) was frequently misperceived as surrounding the preceding or following picture in the sequence (temporal migration; Intraub, 1985, 1989). Would temporal migration of the frame be reduced if the frame and picture shared a common property (colour)? Two different colour frames were created for each picture: one matching and one mismatching the picture's most prevalent colour (Experiment 1) as determined by a computational image colour summarizer (Krzywinski, 2018). Presentation rate was 100 ms/picture. Colour-matching significantly reduced temporal migration (4.3%), but the effect was small. To determine if greater colour-overlap would yield a larger effect, frames composed of colour "tiles" that matched or mismatched each picture's four most prevalent colours were presented at a rate of 111 ms/picture (Experiment 2). Again, a small, significant reduction in temporal migration was observed (3.2%). Although pictures and frames are distinct forms, the probability of correct integration of the two appears to be affected by the presence of a common property (colour). Results are discussed in terms of an integrative short-term buffer. Possible application of the temporal migration paradigm to studying visual integration of components of real-world scenes is addressed.

• Sinead A. Williamson
• Jette Henderson

Understanding how two datasets differ can help us determine whether one dataset under-represents certain sub-populations, and provides insights into how well models will generalize across datasets. Representative points selected by a maximum mean discrepancy (MMD) coreset can provide interpretable summaries of a single dataset, but are not easily compared across datasets. In this paper, we introduce dependent MMD coresets, a data summarization method for collections of datasets that facilitates comparison of distributions. We show that dependent MMD coresets are useful for understanding multiple related datasets and understanding model generalization between such datasets.

• Jack William Penn
• Hani J Marcus
• Christopher E.G. Uff

Connectivity is a driving force for productivity across a wide variety of sectors in the 21st Century with healthcare being no exception. 5th generation cellular technology (5G) is frequently alluded to in the mainstream media but understanding of the technology and its potential impact is not widespread in clinical communities. It promises unprecedented improvement in speed, bandwidth, reliability and latency, all of which have significant implications for the way we use wireless data. 5G can be subdivided into three parallel technological architectures: extended mobile broadband (eMBB), ultra-reliable low latency communication (URLLC), and massive machine type communication (mMTC). These domains each present different and exciting prospects for the future of healthcare. This narrative review aims to elucidate the nature of 5G, its context within the development of telecommunications, and describe some of the notable opportunities it presents to the neurosurgical community. In many cases the requisite hardware has already been developed, but use has been limited by the requirements of a fast, reliable and omnipresent network connection. Examples include telesurgical robots, remote supervision of procedures, integrated smart operating theatres and clinician telepresence. The events of 2020 and the COVID-19 pandemic have brought the world's attention to digital transformation. The mechanics of 5G connectivity creates the capacity for these changes to be applied practically. An understanding of this technology is essential to appreciate the development and opportunities which will be part of our professional future.

Background: ME/CFS is a stigmatised, often misunderstood condition. This situation is compounded by minimal research funding and contested clinical guidance. Use of inaccurate images purporting to represent ME/CFS perpetuates and reinforces biases, preconceptions, misconceptions and stigma. This impedes the influence of emerging research in informing the public, researchers and clinicians about the reality of the condition. Objectives: This poster challenges people to: reconsider their use of images, given the power of images to educate or misinform understand the damaging effect of inappropriate images that contradict or undermine the accompanying text develop an awareness of appropriate images Methods: 1. Search the literature on the comparative power of images and text. 2. Undertake content analysis of inappropriate images of ME/CFS. 3. Search the literature for information on the potential for damage from use of inappropriate images. 4. Undertake content analysis of the use of more accurate visual representations of ME/CFS. Results: Images attract attention, convey complex information rapidly, and enhance retention of associated text. In a search of Google News for articles on research into Chronic Fatigue Syndrome, of the 298 articles found, only 17 contained a realistic depiction of a person with ME/CFS. The remainder involved a missed opportunity or misinformation, often through use of inappropriate stock images. Realistic images can convey stories about ME/CFS that current lay and medical vocabulary struggle to adequately describe. Conclusion: Investment of time and effort to select appropriate images is warranted, given the power of images to either reinforce bias and stigma, or to accurately represent the illness and invoke an emotional investment in the important issues around ME/CFS. Funding: None Off-Label Use: None COI: None Contact: penelope.mcmillan@mecfs.org.au

• Kenneth Forster
• Chris Davis

Six experiments investigated repetition priming and frequency attenuation in lexical access with 164 college students. Repetition priming effects in lexical decision tasks are stronger for low-frequency words than for high-frequency words. This frequency attenuation effect creates problems for frequency-ordered search models that assume a relatively stable frequency effect. It was posited that frequency attenuation is a product of the involvement of the episodic memory system in the lexical decision process. This hypothesis was supported by the demonstration of constant repetition effects for high- and low-frequency words when the priming stimulus was masked; the masking was assumed to minimize the influence of any possible episodic trace of the prime. It was further shown that long-term repetition effects were much less reliable when the S was not required to make a lexical decision response to the prime. When a response was required, the expected frequency attenuation effect was restored. It is concluded that normal repetition effects consist of 2 components: a very brief lexical effect that is independent of frequency and a long-term episodic effect that is sensitive to frequency. (32 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)

• Vincent Di Lollo

The binding problem arises when visual features (colour, orientation), said to be coded in independent brain modules, are to be integrated into unitary percepts. I argue that binding is an ill-posed problem, because those modules are now known to code jointly for multiple features, rendering the feature-binding issue moot. A hierarchical reentrant system explains the emergence of coherent visual objects from primitive features. An initial feed-forward sweep activates many high-level perceptual hypotheses, which descend to lower levels, where they correlate themselves with the ongoing activity. Low correlations are discarded, whereas the hypothesis that yields the highest correlation is confirmed and leads to conscious awareness. In this system, there is no separate binding process that actively assigns features to objects.

When viewing a rapid sequence of pictures, observers momentarily understand the gist of each scene but have poor recognition memory for most of them (M. C. Potter, 1976). Is forgetting immediate, or does some information persist briefly? Sequences of 5 scenes were presented for 173 ms/picture: when yes-no testing began immediately, recognition was initially high but declined markedly during the 10-item test. With testing delays of 2 or 6 s, the decline over testing was less steep. When 10 or 20 pictures were presented, there was again a marked initial decline during testing. A 2-alternative forced-choice recognition test produced similar results. Both the passage of time and test interference (but not presentation interference) led to forgetting. The brief persistence of information may assist in building a coherent representation over several fixations.

Little is known about how attention changes the cortical representation of sensory information in humans. On the basis of neurophysiological evidence, we hypothesized that attention causes tuning changes to expand the representation of attended stimuli at the cost of unattended stimuli. To investigate this issue, we used functional magnetic resonance imaging to measure how semantic representation changed during visual search for different object categories in natural movies. We found that many voxels across occipito-temporal and fronto-parietal cortex shifted their tuning toward the attended category. These tuning shifts expanded the representation of the attended category and of semantically related, but unattended, categories, and compressed the representation of categories that were semantically dissimilar to the target. Attentional warping of semantic representation occurred even when the attended category was not present in the movie; thus, the effect was not a target-detection artifact. These results suggest that attention dynamically alters visual representation to optimize processing of behaviorally relevant objects during natural vision.

• Helene Intraub

When a sequence of pictures is presented at the rapid rate of 113 msec/picture, a viewer can detect a verbally specified target more than 60% of the time. In the present experiment, sequences of pictures were presented to 96 undergraduates at rates of 258, 172, and 114 msec/picture. A target was specified by name, superordinate category, or "negative" category (e.g., "the picture that is not of food"). Although the probability of detection decreased as cue specificity decreased, even in the most difficult condition (negative category cue at 114 msec/picture) 35% of the targets were detected. When the scores from the 3 detection tasks were compared with a control group's immediate recognition memory for the targets, immediate recognition memory was invariably lower than detection. Results are consistent with the hypothesis that rapidly presented pictures may be momentarily understood at the time of viewing and then quickly forgotten. (19 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)

• Marvin M Chun

Visual context information constrains what to expect and where to look, facilitating search for and recognition of objects embedded in complex displays. This article reviews a new paradigm called contextual cueing, which presents well-defined, novel visual contexts and aims to understand how contextual information is learned and how it guides the deployment of visual attention. In addition, the contextual cueing task is well suited to the study of the neural substrate of contextual learning. For example, amnesic patients with hippocampal damage are impaired in their learning of novel contextual information, even though learning in the contextual cueing task does not appear to rely on conscious retrieval of contextual memory traces. We argue that contextual information is important because it embodies invariant properties of the visual environment such as stable spatial layout information as well as object covariation information. Sensitivity to these statistical regularities allows us to interact more effectively with the visual world.

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Source: https://www.researchgate.net/publication/259490307_Detecting_meaning_in_RSVP_at_13_ms_per_picture